头 (traditional 頭) paired 豆 (a sound) with 页 (which itself pictures a head on a body). The simplified 头 is a quick everyday form — think of 大 (big) with two dots, the 'big top' of the body.
头 is the head, and by extension the top or chief of things: 回头 (turn one's head / later on, with 回), 头发 (hair, 'head-hair'), 前头/后头 (front/back, with 前/后). As 'chief': 头儿 (the boss). It's also a common noun-suffix that makes things concrete and rounded: 木头 (wood — you learned this!), 石头 (stone), 馒头 (steamed bun) — in this use it's toneless (tou). From the top of your body to the head of a group, 头 sits on top.
The 'big top' of the body — the HEAD.
头 is also a toneless suffix making nouns concrete: 木头 (wood — you know it!), 石头 (stone), 馒头 (steamed bun). 头大 ('head big') means feeling overwhelmed.