Abihu in Easton's Bible Dictionary

father of Him; i.e., "worshipper of God", the second of the sons of Aaron (Ex. 6:23; Num. 3:2; 26:60; 1 Chr. 6:3). Along with his three brothers he was consecrated to the priest's office (Ex. 28:1). With his father and elder brother he accompanied the seventy elders part of the way up the mount with Moses (Ex. 24:1,9). On one occasion he and Nadab his brother offered incense in their censers filled with "strange" (i.e., common) fire, i.e., not with fire taken from the great brazen altar (Lev. 6:9, etc.), and for this offence they were struck dead, and were taken out and buried without the camp (Lev. 10:1-11; comp. Num. 3:4; 26:61; 1 Chr. 24:2). It is probable that when they committed this offence they were intoxicated, for immediately after is given the law prohibiting the use of wine or strong drink to the priests.

Link: https://bible-history.com/eastons/A/Abihu/