Radical choice for 安全
Splitting the character 安, we get 宀 + 女.

In oracle bone script, 宀 stands for house, and 女 means bride. The whole caracter means "bride in new house" (i.e. marriage).

In traditional Chinese culture, marrying a girl is a huge settlement in a man's life, so 安 means 安定 (settled), 安心 (relieved).

Reference is in full Chinese (so it's a bit hard for learners to read).