c. 1500, "reflection of light, image produced by reflection," from a verb reflex meaning "refract, deflect" (late 14c.; compare reflect), from Late Latin reflexus "a bending back," noun use of past participle of reflectere "to bend back, bend backwards, turn away," from re- "back" (see re-) + flectere "to bend" (see flexible). Also as an adjective (1640s), "thrown or turned backward," also of thoughts or the mind. Meaning "involuntary nerve stimulation" is recorded by 1877, short for reflex action (1833) "simple, involuntary action of the nervous system."
1620s, "to drive away by calling 'shoo,' " from the exclamation (late 15c.), perhaps instinctive, compare German schu, Italian sciò. Related: Shooed; shooing.
"an instinctive stretching of oneself, as upon awakening," 1610s, noun of action from past-participle stem of Latin pandiculari "to stretch oneself," from pandere "to stretch" (from nasalized form of PIE root *pete- "to spread"). Sometimes used inaccurately for "a yawning."
1580s, "reflective, capable of bending or turning back," from Medieval Latin reflexivus, from Late Latin reflexus (see reflect). Meaning "of the nature of a reflex" is from 1839 (implied in reflexively). Grammatical sense, in reference to verbs especially, "turning the action back upon the subject," is by 1740. Related: Reflexiveness; reflexivity.
1817, "inclined to the production of offspring, fond of children," irregularly formed from philo- + Latin progenit-, past-participle stem of progignere (see progeny). Philoprogenitiveness "the love of offspring, instinctive love of the young in general" is from 1815. Both first attested in translations of Spurzheim and important words among the phrenologists. Related: Philoprogeneity.