借

Person radical on the left makes the social context explicit: borrowing and lending only happen between people. It indexes 借 in the human-action family alongside 信 to trust, 偿 to repay, 价 price. The radical reminds the learner that this is a transaction between two people — exactly why 借 carries both directions of the lending arrow.

Right is 昔 'in former days', supplying the sound — xī drifting to jiè via standard x/j alternation. Same phonetic in 错 mistaken, 措 to handle, 籍 register. 昔 itself shows layered days (a sun beneath ancient overlapping graphs); a faint 'something owed across time' flavor fits a loan that will eventually return.