inch (n.1) Look up inch at
"linear measure, one-twelfth of a foot," late Old English ynce, Middle English unche (current spelling c. 1300), from Latin uncia "a twelfth part," from unus "one" (see one). An early Anglo-Saxon borrowing from Latin; not found in other Germanic languages. Transferred and figurative sense of "a very small amount, small quantity" is attested from mid-14c. As the unit of measure of rainfall from 1845. Sometimes misdivided in Middle English as a neynche. Every inch "in every respect" is from early 15c. For phrase give him an inch ... see ell.
inch (n.2) Look up inch at
"small Scottish island," early 15c., from Gaelic innis (genitive innse) "island," from Celtic *inissi (source also of Old Irish inis, Welsh ynys, Breton enez).
inch (v.) Look up inch at
1590s, "move little by little" (intrans.), from inch (n.1). Meaning "drive or force by small degrees" (trans.) is from 1660s. Related: Inched; inching.