help, support, assist, aid
贊 centers on giving active support: helping, assisting, or aiding someone or something. The idea of offering help is the core, with all given meanings flowing from that.
贊 combines 兟 (a doubled form of 先, suggesting forward movement or presentation) with 貝 (shell, money), likely expressing the idea of offering valuables or support. The exact historical development is uncertain, but the component structure points to presenting aid or tribute.
The top part 兟 looks like two people stepping forward, and the bottom 貝 is a shell (money). Picture two people stepping forward with shells to help someone in need: 贊 means help and support.
For サン, imagine a helpful person named San stepping forward with shells to assist: San -> サン, and San's help is the core of 贊.