• 端はし — edge; end; tip; corner
• 端はた — side; edge (in some dialects / set phrases)
• 先端せんたん — the very tip; forefront
• 両端りょうたん — both ends
• 端的たんてき — direct; to the point
• 極端きょくたん — extreme
• 発端ほったん — the start; the trigger; the origin of something

The top part is 立（たつ） — “to stand.” The lower part shapes the sound (タン). Picture something standing upright at the very edge, right at the boundary. That’s 端: the end, the border, the outermost point where something begins or finishes.