Wilt

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late 17th century (originally dialect): perhaps an alteration of dialect welk ‘lose freshness’, of Low German origin.

wiktionary

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Recorded since 1691, probably an alteration of welk, itself from Middle English welken, presumed from Middle Dutch (preserved in modern inchoative verwelken) or Middle Low German welken(“to wither”), cognate with Old High German irwelhen(“to become soft”).

wilt

etymonline

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wilt (v.)

1690s, "to fade, droop, wither," probably an alteration of welk "to wilt," probably from Middle Dutch or Middle Low German welken "to wither," cognate with Old High German irwelhen "become soft," from Proto-Germanic *welk-, from PIE root *welg- "wet" (see welkin). Transitive sense of "cause to fade or droop" is from 1809. Related: Wilted; wilting.