In the Hebrew Scriptures, the word jam designates the husband’s father (Ge 38:13, 25; 1Sa 4:19, 21), and in feminine gender, ha mohth, the husband’s mother, that is, the mother-in-law of the husband. Wife. (Ruth 1:14; Mic 7:6.)
The Hebrew verb cha·thán means “to form a marriage alliance.” (De 7:3; 1Sa 18:20-27; 1Ki 3:1; 2Ch 18:1) The husband’s father-in-law, that is, the wife’s father, is designated by a masculine participle of the Hebrew verb ha· than. This same participle, but in feminine, refers to the mother-in-law. (De 27:23)
The engaged couple was seen as already married even though the marriage had not yet taken place, so the woman was considered the man’s wife. (Jg 14:20) Consequently, the man was called “son-in-law” (a name derived from ha·than was used), regardless of whether the marriage covenant had been made.—Jg 19:5; 1Sa 22:14; Ne 6:18; 13:28) or contemplated doing so, as in the case of Lot’s “sons-in-law.” (Ge 19:12, 14; compare Jg 15:6.) Lot’s daughters were only betrothed, otherwise they would live with their husbands and not in their father’s house. Further proof that the two men were only future sons-in-law (engaged to Lot’s daughters but not yet married to them) is the fact that, as most English versions indicate, the Hebrew allows the verse to be translated as follows: “His sons-in-law who were to take his daughters.” (Ge 19:14, Mod, note; NM; Val; compare BAS, BJ, LT, RH, etc.)
In the Christian Greek Scriptures pen·the·ros·s is translated “father-in-law” (Jn 18:13), and its feminine form, pen·the·raʹ, “mother-in-law.” (Mt 8:14; 10:35; Mr 1:30; Lu 4:38; 12:53; see DAUGHTER-IN-LAW.)
Source: Dictionary of the Bible
pentheros (penqerov”, 3995), father of the wife (from a root meaning bond, union). It is found in Joh 18:13:¶
Source: Vine New Testament Dictionary