An Etymological Dictionary of the German Language/pflegen
pflegen, vb., ‘to nurse, cherish, indulge in, be accustomed to,’ from MidHG. pflëgen, OHG. pflëgan, ‘to take care of, take a friendly interest in, provide for, protect, carry on, be wont or accustomed to,’ OHG. and early MidHG. also ‘to promise, stand security for.’ It corresponds to OSax. plëgan, ‘to promise, stand security, be answerable for,’ Du. plegen, ‘to nurse, execute, do, be accustomed’; also to AS. plëgian, ‘to move on rapidly, play,’ E. to play. The Prov. and OFr. plevir, ‘to assure, stand security,’ to which no definite Lat. and Rom. original can be assigned, is derived rather from MidEurop. Teut. (OSax. and OHG.) than the reverse. E. pledge originated in OFr. pleige, MidLat. plegium. Although the West Teut. cognates must have existed perhaps as early as the 4th cent., 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 Gr. βλέφαρον, ‘eye,’ as well as βλέπειν, ‘to see’ (Aryan root glegh?), is perhaps primit. allied. If the cognates have been borrowed, their source cannot be determined; Rom. is out of the question, since it contains no suitable root from which they can be derived. See Pflicht.