Old English torr "tower, watchtower," from Latin turris "a tower, citadel, high structure" (also source of Old French tor, 11c., Modern French tour; Spanish, Italian torre "tower"), possibly from a pre-Indo-European Mediterranean language. Meaning "lofty pile or mass" is recorded from mid-14c. Also borrowed separately 13c. as tour, from Old French tur; the modern spelling (1520s) represents a merger of the two forms.
c. 1400, "rise high" (implied in towered); see tower (n.). Also, of hawks, "to fly high so as to swoop down on prey" (1590s). Related: Towering.
"one who tows," 1610s, agent noun from tow (v.).