The Hebrew noun אב (av, pronounced AHV, with the Hebrew letter "bet" pronounced like a "v") is the word for "father" or "ancestor." So when Exodus 20:12 says, "Honor your father (אביך) and mother," it is using the same word, אב (av), as in Genesis 4:20: "Adah bore Jabal; he was the ancestor (אבי) of those who live in tents and have livestock." Thus, Biblical Hebrew uses the word אב (av) in a manner similar to the English word "forefather."