Originally transitive in English; long obsolete in this sense but somewhat revived in digital gaming via "fear" spells, which matches the old sense "drive away by fear," attested early 15c. Meaning "feel fear" is late 14c. Related: Feared; fearing.
mid-15c., "concealed, secret," from Latin latentem (nominative latens) "lying hid, concealed, secret, unknown," present participle of latere "lie hidden, lurk, be concealed," from PIE *late-, suffixed form of root *lādh- "to be hidden" (source also of Greek lēthē "forgetfulness, oblivion," lēthargos "forgetful," lathre "secretly, by stealth," lathrios "stealthy," lanthanein "to be hidden;" Old Church Slavonic lajati "to lie in wait for"). Meaning "dormant, undeveloped" is from 1680s, originally in medicine.
Meaning "professed lover, one devoted to the service of a lady" is from mid-14c. In North American colonies and U.S., the usual designation for "slave" 17c.-18c. (in 14c.-15c. and later in Biblical translations the word often was used to render Latin servus, Greek doulos "slave"). Public servant is attested from 1670s.
Old English colian, "to lose warmth," also figuratively, "to lose ardor;" cognate with Old Saxon kolon, Dutch koelen, Old High German chuolan, German kühlen, all from the root of cool (adj.). Transitive meaning "to cause to lose warmth, reduce the temperature of" is from late 14c. Related: Cooled; cooling.
Figurative meaning "abate the intensity of" is from c. 1300. To cool (one's) heels" wait in attendance, "generally applied to detention at a great man's door" [Century Dictionary] is attested from 1630s; probably the notion is "to rest one's feet after walking."