An Etymological Dictionary of the German Language/Annotated/Frist
Frist, feminine, ‘period, appointed time, respite,’ from Middle High German vrist, feminine, Old High German frist, feminine, (neuter), ‘limited period, postponement, space of time’; Old Saxon frist, Anglo-Saxon first, masculine, Old Icelandic frest, neuter plural, ‘postponement.’ Probably not derived from the root fri (see frei), ‘to love.’ It might more reasonably be connected with the Gothic verbal particle fri in frisahts, if the meaning of the latter were clear. See also Rist