KanjiJLPT N2
Arm

arm, ability, talent

Mnemonic

Under the moon, a glowing envelope addressed to you crashes at your feet. You rip it open and a muscular arm bursts out, flexing with incredible skill — the moon's own arm, gifted to you for its strength.
Additional thoughts
Picture the moon literally ripping off its own arm, packaging it, and mailing it to you. Moon = body radical, addressed to = delivery. Together they form a powerful, skilled arm of lunar origin.
Quick recall
A package addressed to you from the moon contains a mighty arm.

Details

The keyword for 腕 is arm. This kanji refers to the physical arm of the human body, typically the section from the shoulder to the hand. Beyond its literal anatomical meaning, it is also commonly used figuratively to denote one's skill, ability, or competence, as in the idea of having a "strong arm" in a particular craft or profession. This dual usage makes it a versatile character in both physical and abstract contexts.
On'yomi
わん
Kun'yomi
うで