働=人 + 動。
人 means “man”, 動 means “to move”.
If you want to work, you need to move.
So 働 stands for “to work”.
Note: Below is the origin and development of kanji 動.
You can see a man who is carrying a big bag.
You need to move in order to carry this bag to other place.
So 動 stands for “to move”.