Comments:EDT 277, ЭСТЯ 1, 383-385, 646, 647, VEWT 175, Егоров 79, 75. There exists a verbal derivative *īŕ-te- 'to follow one's tracks', attested as iste- as early as in OUygh. (see EDT 243) and in many modern languages (see ЭСТЯ 1, 383); but simultaneously there is a variant *īr-te- (with *-ŕ- > -r- according to Helimski's rule), attested already in MK (see EDT 208) and in Yak., Dolg. irdē-, see Stachowski 128.