Aside from “back,” “stature,” and “height,” 背 can mean “behind, to disobey, to defy, to go back on, to rebel.” I suppose a great deal can go on behind our backs! Here are some betrayal expressions including 背:
背信 (haishin: betrayal, infidelity)
to disobey + fidelity背反行為 (haihankōi: act of disobedience (betrayal), infraction)
to disobey + anti- + conduct (last 2 chars.)The last two kanji, 行為, break down further as to go + to do.
背徳 (haitoku: adultery, corruption, lapse from virtue)
to go back on + benevolence背任 (hainin: (legal) breach of trust)
to disobey + responsibility
