The Proto-Indo-European word *yenh₂ter-
Word *yenh₂ter-
Meaning brother-in-law's wife
See also Homeric Greek: εἰνάτερες ‘wives of brothers’

Comments
Lat. ianitrīcēs, Gk. einatēr, Lith. jentė, Ltv. ietere, Russ. jatrov', Skr. yātar, Kamviri iâri, Arm. ner, Phryg. ianatera, Polish jątrew

Other words that might be of interest
*bʰréhater- ‘brother’, *ĝ(e)lōu̯- ‘sister in law’, *gʷénha ‘woman, wife’, *i̯énǝter- ‘husband’s brother’s wife’, *méhₐtēr ‘mother’, *aner-, ner- ‘man, vital energy’, *awo- ‘grandfather, adult male relative other than one's father’, *deh₂iwer- ‘husband's brother’, *dhuĝ(hₐ)tḗr ‘daughter’, *ĝh₂lōu- ‘brother's wife’, *h₂en- ‘ancestor’, *népot- (nom. népōt-s gen. nept-ós) ‘grandson/nephew’, *ph̥atḗr ‘father’, *snúso- ‘daughter-in-law’, *swésōr ‘sister’, *wihₓrós ‘husband, man, freeman’, *at- ‘father’, *dheh₁- ‘uncle’, *h₂euh₂os ‘uncle, grandfather’, *h₂/₃orbʰos ‘orphan, heir’, *h₂/₃wed(h₂)- ‘lead in marriage, marry’, *h₄em- ‘mother’, *h₄en- ‘mother, (old) woman’, *hₐekkehₐ- ‘mother’, *hₐnḗr ‘man, person’, *t-at- ‘father’, *wersēn ‘male’, *manu- ‘man, ancestor of humankind’, *m-h₄em- ‘mother’, *népōts ‘grandson, nephew’, *n-h₄en- ‘(old) woman, mother’, *papa ‘father, papa’, *pótis ‘husband’, *r̥sḗn ‘male’, *sm̥-loghos ‘spouse’, *sneubʰ- ‘marry’, *swék̂uros ‘father-in-law’, *bʰrehatríyom ‘brotherhood’, *dhĝhm̥ón- ‘man’, *ĝénh₁es- ‘family’, *ĝenh₁tōr ‘father, procreator’, *ĝenh₁trihₐ- ‘mother, procreatrix’, *mr̥tós ‘dead, mortal’, *mórtos ‘person, mortal, man’, *neptihₐ- ‘granddaughter, (?) niece’, *neptiyos ‘descendant’, *putlós ‘son’, *potnihₐ- ‘mistress, lady, wife’, *prihₓehₐ ‘wife’, *suhₓsos ‘grandfather’, *suhₓyús ‘son’, *suhₓnús ‘son’, *swek̂rúhas ‘mother-in-law’, *teknom ‘child, offspring’, *widhewehₐ ‘widow’