首

1. Origins, structure, and basic meaning

• Structure: 首 (くび) is a noun for the neck, also used idiomatically for dismissal from employment.
• Basic usage: 首が痛くなる names the body part hurting after desk work, while 会社を首になった uses the noun in an idiom for being dismissed after rule violations.

2. Common pitfalls and similar expressions

• Body part and dismissal idiom
  • 首になる is an idiomatic construction meaning dismissal, not a literal change in one’s neck. 会社を identifies the organization the person is made to leave.