The same root (with Ablaut and old morphonological changes) is present in two PN derivates:
1) *šir-i(n) "old (of age)" > Chech., Ing. šira, Bacb. širĩ;
2) *t-iš-i(n) "old (inanim.)" > Chech., Ing. tiša, Bacb. tišĩ.