In the primitive age (even today in some aborigins), counting objects more than 3 is beyond their mathematical capability. Trees are used to denote the maximum Big Number ‘3’, hence Three and ‘Trois’ (French).
Chinese character 3 is 三: 3 tree logs stacked up, starting from 1 (一) to 2 (二) to 3 (三).
Beyond three, Chinese primitives said there are too many, cannot count but only ‘see’, so 4 is 四 = eye (目). Coincidently 4 is pronounced as ‘si’, and is another character ‘视’ meaning ‘see’. (See my previous blog on “Half-life”
Chinese adjectives describing the word “Many” is 3 or 3 items. Example: 3 people (人: image of a man walking with 2 legs) is 三人。Many people is 众 (3 people stacked up).
Confucius said “there is surely a teacher amongst 3 people” 三人行必有我师。He meant among a group of many people (more than 3), surely emerge a leader / teacher.