Is it ensure, insure, or assure?
"an upper chamber," c.1300, from late Old English loft "the sky; the sphere of the air," from Old Norse lopt "air, sky," originally "upper story, loft, attic" (Scandinavian -pt- pronounced like -ft-), from Proto-Germanic *luftuz "air, sky" (cf. Old English lyft, Dutch lucht, Old High German luft, German Luft, Gothic luftus "air").
Sense development is from "loft, ceiling" to "sky, air." Buck suggests ultimate connection with Old High German louft "bark," louba "roof, attic," etc., with development from "bark" to "roof made of bark" to "ceiling," though this did not directly inform the meaning "air, sky." But Watkins says this is "probably a separate Germanic root." Meaning "gallery in a church" first attested c.1500.
"to hit a ball high in the air," 1856, originally in golf, from loft (n.). Related: Lofted; lofting. An earlier sense was "to put a loft on" (a building), 1560s; also "to store (goods) in a loft" (1510s).