From Middle Low German bôchêm, bôkhêm, equivalent to bôke, bö̂ke (“beech”) + hêm (“home”). Compare -um (placename suffix). The [x] may go back to spelling pronunciation or influence by a Central German dialect. (It could also be a native development [kh] → [x] as in Dutch lichaam, but the popular form in Westphalian Low German is Baukem.) Doublet of Buchheim.