契る

1. Origins, structure, and basic meaning

• Structure: 契る(ちぎる) is a verb meaning to make a firm pledge or vow.
• Basic usage: It is used for weighty promises, such as pledging mutual help or enduring love.

2. Common pitfalls and similar expressions

• Different from an everyday promise
  • It has a more solemn or literary tone than 約束する(やくそくする), so it is not a straightforward substitute for making a casual appointment.
• と marks the content of the pledge
  • In 助け合うと契った, と marks the promise to help each other.
  • 契った is the past form of 契る; it does not mean that the promise has already been fully carried out.