early 14c., "a crutch," a common Germanic word (cognates: Danish stylte, Swedish stylta, Middle Low German, Middle Dutch stelte "stilt," Flemish stilte "stick," Old High German stelza "plow handle, crutch"), though the exact relationship of them all is unclear, from Proto-Germanic *steltijon, from extended form of PIE root *stel- "to put, stand, put in order," with derivatives referring to a standing object or place.
Application to "wooden poles for walking across marshy ground, etc." is from mid-15c. Meaning "one of the posts on which a building is raised from the ground" is first attested 1690s. As a type of bird with long legs, from 1831. Stilted in the figurative sense of "pompous, stuffy" is first recorded 1820.