Definitions of swear:

• verb:   promise solemnly; take an oath
• verb:   make a deposition; declare under oath
• verb:   have confidence or faith in

  Example: "I swear by my grandmother's recipes"

• verb:   utter obscenities or profanities
• verb:   to declare or affirm solemnly and formally as true

  Example: "Before God I swear I am innocent"