spoon, key
鍉 centers on a metal tool with a dual purpose: a spoon for scooping or a key for unlocking. The two meanings likely reflect different historical uses of the same metal implement.
鍉 combines 金 (metal) with 是, which likely contributes the sound. The character originally referred to a metal spoon or key, but the exact historical development is uncertain.
The left side is metal 金, and the right side 是 looks like a straight object with a handle. Picture a metal spoon that can also be used as a key to open a container.
For テイ, imagine a metal spoon being used to stir a cup of tea: tea -> テイ, and the spoon is made of metal.