北极
běi jí · HSK 5
north pole
🧭❄️ 北极 = north + extreme/pole
北 means north; 极 means extreme end or pole (same 极 as in 极端 'extreme'). So 北极 is literally 'north pole' — both the geographic Arctic and the magnetic north pole.
北 — two people 人 back-to-back
北 originally pictured two people standing back-to-back, meaning 'back' or 'to turn one's back on.' Because people in ancient China faced south, their backs pointed north, so 北 came to mean 'north.' The original 'back' sense was later written with 背 (adding 月/flesh).
极 — wood radical 木 + 及 (jí, phonetic)
极 is a semantic-phonetic compound: 木 (wood) hints at the meaning, since the original sense was the ridgepole — the highest beam of a roof. 及 supplies the sound 'jí'. From 'topmost beam' the meaning extended to 'extreme, utmost, pole', as in 北极 (North Pole).