According to Etymonline,I can't help wondering whether there is any other example like this? Because E."emmet",which preserves the "m" intactly,is the cognate of E."ant",which "changed" the "m" to "n" and is "contracted"?
ant (n.) c.1500, from Middle English ampte (late 14c.), from O.E. æmette "ant," from W.Gmc. *amaitjo (cf. O.H.G. ameiza, Ger. Ameise) from a compound of bases *ai- "off, away" + *mai- "cut," from PIE *mai- "to cut" (cf. maim). Thus the insect's name is, etymologically, "the biter off." As þycke as ameten crepeþ in an amete hulle [chronicle of Robert of Gloucester, 1297] Emmet survived into 20c. as an alternative form. White ant "termite" is from 1729. To have ants in one's pants "be nervous and fidgety" is from 1934, made current by a popular song; antsy embodies the same notion.
emmet "ant," from O.E. æmete (see ant), surviving as a dialect word in parts of England; also, in Cornwall, a colloquial name for holiday tourists.