This curve shows a point of maximum temperature at F1, and a retroflex portion F1G1.
The retroflex sibilant is transliterated sh; this was unchanged.
This curve also shows a point of maximum temperature (F) and a retroflex portion.
1776, from Modern Latin retroflexus, past participle of retroflectere "to bend back," from retro (see retro-) + flectere "to bend" (see flexible). The verb (1898) is a back-formation from retroflexed (1806), from the adjective.