The biblical spelling is "Mehetabel"; an English spelling variation is "Mehitabel"; "Mehitable" is a misspelling.

1.  Frederick W. Bailey.  1896-1906.  Early Connecticut Marriages, as Found in Ancient Church Records, Prior to 1800.  7 vols.  Bureau of American Ancestry, New Haven, CT (mostly records of Congregational Churches, with a few Episcopalian Churches; republ. 1997 by Genealogical Publ. Co., Baltimore, MD; online at Ancestry.com):

p. 81

POMFRET... Nehemiah Lyon of Woodstock & Mehitabel Squire, Dec. 18, 1794

I have no explanation here beyond the fact that Bailey may have erred.  If he didn't, what is the explanation?

2.  A.B. Lyon, G.W.A. Lyon, & Eugene F. McPike.  1905. Lyon Memorial.  Vol. I.  Press of Wm. Graham Printing Co., Detroit, MI (online at GenealogyLibrary.com in OCR version with many recognition errors and at Ancestry.com as page images):

p. 52	70. IV. 11. NEHEMIAH4 LYON [William3, John2, William1] was born in Woodstock, Conn., Oct. 16, 1719, and died there Oct. 1, 1807; buried in East Woodstock cemetery.  He married first, in Woodstock, July 3, 1741 [July 2, T.R.], Mehitable Child, who was born in Woodstock,
p. 53	Jan. 15, 1719 (T.R.) [Jan. 19, Mss. Fam. Record] and died April 13, 1789 "at 27 minutes after 9 o'clock, ae. 70 y. 2 m. 27 d." (T.R.) [d. April 17, 1780 (?), ae. 70 y., G.R.]  She was daughter of Ephraim§ and Priscila (Harris) Child, of Roxbury, Mass.  Nehemiah married second, Dec. 18, 1794, in Pomfret, Widow Elizabeth Squiers, of Pomfret [T.R.].  She was born in 1731 and died Nov. 12, 1804 [Woodstock T.R.].  Nehemiah Lyon was a prominent citizen of Woodstock.  He took the freeman's oath in 1749.  He was selected to convey to the General Assembly the protest of his district against the Stamp Act in 1765, and during the Revolution he, with his nephew, Capt. Benjamin Lyon, were appointed to receive and transmit donations for the relief of Boston.  He was deputy from Woodstock 1762-1769.  In 1768 he was one of five appointed to invite Rhode Island to "appear in person" before the General Assembly of Connecticut and unite in asking to have the Massachusetts boundary line settled.  In 1771, at a meeting held in the house of Colonel Israel Putnam, he was one of four to represent Woodstock in a conference with representatives from Killingly, Thompson Parish, Ashford and Union in regard to some "new bound for the county."  He was, moreover, deacon in the First Church of Woodstock.  Children of Nehemiah and Mehitable (Child) Lyon, born in Woodstock:      216.   I.   Martha, b. April 24, 1742 (T.R.); bapt. April 25, 1742 (Ch.R.); m. Dec. 27, 1770, Eliakim May (T.R.)†; d. May 6, 1813.   217.   II.   Elisha, b. Feb. 11, 1744 (T.R.); bapt. Feb. 12, 1744 (Ch.R.); killed by accidental discharge of a gun at a training, Oct. 15, 1767 (T.R.).   *218.   III.   Amasa, b. July 23, 1745 (T.R.); bapt. July 28, 1745 (Ch.R.); d. at Pollet, Vt., Oct. 12, 1776; ae. 31 y. (G.R., E. Woodstock Cemetery).   *219.   IV.   Aaron, b. Dec. 5, 1747 (T.R.); bapt. Jan. 31, 1748 (Ch.R.); d. Oct. 28, 1821, ae. 74 (G.R., East Woodstock Cem.). ... §Ephraim (4) Child; son of Benjamin (3) and Grace (Morris) Child  [Ephraim (2); Benjamin (1)].  †Eliakim May was born in 1742 and died March 27, 1816...
p. 54	220.   V.   Levina,§ b. Aug. 7, 1750; bapt. Aug. 12, 1750 (Ch.R.); m. Jan. 14, 1773, Peleg Corbin*** (T.R.); d. Nov. 18, 1788 (T.R.).   *221.   VI.   Lyman, b. March 10, 1753 (Bible R.) [March 11, T.R.]; bapt. (date not found); d. Stafford, Conn., Feb. 3, 1??24, ae. 71 (G.R.).   222.   VII.   Eliakim, b. Nov., 1755 [T.R. gives "Liakim" without date]; bapt. Nov. 16, 1755 (Ch.R.); d. 1776 (T.R.).   223.   VIII.   Mehitable, b. Aug. 14, 1758 (T.R.); bapt. Aug. 20, 1758 (Ch.R.); m. April 10, 1777, Samuel Corbin, Jr. (T.R.)‡; d. before 1781. ... §The Hartford Courant, Jan. 6, 1766, had this Item: Miss Levina Lyon, daughter of Capt. Nehemiah Lyon of Woodstock, and Miss Molly Ledoit carded and spun in one day 22 skeins of good tow yarn and a few days after, Martha, sister of Levina, spun 194 knots of good linen yarn  in one day."  ***Peleg (4) Corbin [Samuel (3), James (2), Clement (1)] was born Sept. 7, 1749.  He was a soldier in the Revolution: one of the pioneers of Thompson, Conn., where he was school teacher and officeholder; removed to Woodstock about 1814.  Children of Peleg and Levina (Lyon) Corbin, b. Thomson, Conn.: 1. Patty, b. April 27, 1774; not m.; d. 1844; 2. Priscilla, b. 1775; m. Nov. 28, 1797, Rensselaer Child (5 sons and 4 daughters); 3. Eliakim Lyon, b. Oct. 7, 1777; m. and had 4 sons and 2 daughters; 4. Ichabod, b. Nov. 13, 1779; 5. Aaron, b. Dec. 15, 1781; m. Betsey Johnson; 6. Horace, b. Oct. 23, 1783; d. Dudley, Nov. 13, 1802 (G.R.); 7. Levina, b. Aug. 11, 1786; m. _____ Perrin; 1 daughter, Polly; 8. Samuel, b. Nov. 5, 1788.  [By his second wife, Peleg had five daughters, making 13 children in all.]  ‡Samuel Corbin was brother of Peleg.  See foregoing note.  He was born Aug. 27, 1751, and died June 9, 1785.  He was a soldier in the Revolution and lived in Woodstock and Dudley.  Mehitable seems to have had no children.  Samuel married, second, Jan. 18, 1781, Lucy Learned, and had one son, Learned, and two daughters, Mehitable (Butler) and Lucy (Brown).

3.  Elias Child.  1881.  Genealogy of the Child, Childs and Childe Families, of the Past and Present in the United States and the Canadas, from 1630 to 1881.  Self-published.  Curtis & Childs, Printers, Utica, NY (online at Ancestry.com).

p. 198

[Fourth Generation.] 31. v. MEHITABLE CHILD, fifth child and second dau. of Ephraim and Priscilla Harris Child, b. in Woodstock, Ct., June 8, 1718, m. July 3, 1741, Nehemiah Lyon, b. 1719, in Woodstock, Ct. [Fifth Generation.] Children:   1067.   i.   MARTHA LYON, b. in Woodstock, Ct., 1742, m. Eliakim May.   1068.   ii.   Elisha LYON, b. in Woodstock, Ct., 1744, d. 1767, by the accidental discharge of a gun at a military training.   1069.   iii.   AMASA LYON, b. in Woodstock, Ct., 1745; m. Martha Dana.   1070.   iv.   AARON LYON, b. in Woodstock, Ct., 1748, m. Elizabeth May; no children.   1071.   v.   LEVINA LYON, b. in Woodstock, Ct., 1750, m. Peleg Corbin; d. 1788.   1072.   vi.   LYMAN LYON, b. in Woodstock, Ct., 1853, m. Hannah Corbin, 1777.   1073.   vii.   MEHITABLE LYON, b. in Woodstock, Ct., 1758, m. Samuel CORBIN.

4.  WorldConnect / Ancestry World Trees (online at RootsWeb.com/Ancestry.com).