An Etymological Dictionary of the German Language/straff
straff, adj., ‘stretched, tense, tight,’ from MidHG. (rare) straf(ff), ‘tense, strict’; probably a LG. word corresponding to Du. straf. Its early history is, however, obscure. It has been supposed that Ital. strappare, ‘to tear out,’ is borrowed from Teut. by assuming a root strap, ‘to draw’; hence straff, lit. ‘drawn tight’?.