Affinitas Affinitatis
The Cyclopedic Law Dictionary · Walter A. Shumaker and George Foster Longsdorf; ed. James C. Cahill · 1922
The Cyclopedic Law Dictionary
That connection between parties arising from marriage which is neither consanguinity nor affinity. This term intends the connection between the kinsmen of the two persons married, as, for example, the husband's brother and the wife's sister.
Ersk. Inst. 1. 6. 8.