restrain
扞 centers on holding back or stopping something: restraining, checking, or preventing movement or action.
扞 combines the hand radical 扌 with 干, which likely contributes both sound and the idea of a shield or defense, suggesting restraining with the hand.
The hand radical 扌 beside 干 (which can suggest a shield or a pole) gives the image of a hand holding a barrier to restrain or block something.
For カン, imagine a hand holding a can firmly to restrain it from rolling away: can -> カン, and the hand keeps it in check.
mutual incompatibility; mutual rejection