Английский Этимологический словарь - lap (n.)

- O.E. lжppa "skirt or flap of a garment," from P.Gmc. *lapp-. Sense of "lower part of a shirt" led 13c. to "upper legs of seated person." Lap (v.) "to lay one part over another" is from the noun. The sense of "take a turn around a track" first recorded 1840s, on notion of "overlapping." Lapdog is from 1645; figurative sense of "subservient person" is from 1980s. Lap dance (1990s) is defined thus in the "New Yorker": "To lap dance, you undress, sit your client down, order him to stay still and fully clothed, then hover over him, making a motion that you have perfected by watching Mister Softee ice cream dispensers."