What's an intuitive derivation behind ODO's definition 1 that helps to remember its meaning:
1. circumscribe = Restrict (something) within limits:
Etymonline: late 14c., from Latin circumscribere "to make a circle around, encircle, draw a line around; limit, restrain, confine, set the boundaries of," from circum- "around" (see circum-) + scribere "write" (see script (n.)). Related: Circumscribed; circumscribing.
Yet how does the idea of 'writing around' something restrict that something?