An Etymological Dictionary of the German Language/Annotated/pflegen
pflegen, verb, ‘to nurse, cherish, indulge in, be accustomed to,’ from Middle High German pflëgen, Old High German pflëgan, ‘to take care of, take a friendly interest in, provide for, protect, carry on, be wont or accustomed to,’ Old High German and early Middle High German also ‘to promise, stand security for.’ It corresponds to Old Saxon plëgan, ‘to promise, stand security, be answerable for,’ Dutch plegen, ‘to nurse, execute, do, be accustomed’; also to Anglo-Saxon plëgian, ‘to move on rapidly, play,’ English to play. The Provençal and Old French plevir, ‘to assure, stand security,’ to which no definite Latin and Romance original can be assigned, is derived rather from Middle European Teutonic (Old Saxon and Old High German) than the reverse. English pledge originated in Old French pleige, Middle Latin plegium. Although the West Teutonic cognates must have existed perhaps as early as the 4th century, nothing definite can be asserted concerning their origin and their numerous meanings, the base of which seems to be ‘to act affectionately for, or in conjunction with, some one’; to this Greek βλέφαρον, ‘eye,’ as well as βλέπειν, ‘to see’ (Aryan root glegh?), is perhaps primitively allied. If the cognates have been borrowed, their source cannot be determined; Romance is out of the question, since it contains no suitable root from which they can be derived. See Pflicht.