'Set' is the causative of 'sit' — 'to cause to sit.' With 430+ OED senses, it is the most polysemous English word.
To put, place, or fix in a specified position or state; to establish or determine.
From Old English 'settan' meaning 'to cause to sit, put in a place, fix, establish,' the causative form of 'sittan' (to sit). From Proto-Germanic *satjaną (to set, cause to sit), causative of *sitjaną (to sit), from PIE root *sed- (to sit). The fundamental relationship is: 'sit' is what something does; 'set' is what you make something do. This sit/set pair represents
'Set' holds the record for the English word with the most definitions in the Oxford English Dictionary — over 430 senses for the verb alone, making it the most polysemous word in English. Yet its origin is beautifully simple: it is just the causative of 'sit.' To set something is to make it sit.