Английский Этимологический словарь - incline (v.)

- early 14c., from O.Fr. encliner, from L. inclinare, from in- "in" + clinare "to bend," from PIE *klei-n-, suffixed form of *klei "to lean." Metaphoric sense of "mental disposition" is c.1600 in Eng. (but existed in classical L.), much earlier than that of "slant, slope" (1846).