The slang term phat is applied to voluptuous large women, with the backronyms pretty hot and thick or pretty hot and tempting.

The proper English word fat can mean obese, or can refer to the chemical compounds to which carbohydrates are converted (fats).

No. That meaning is known as a "backronym" or an acronym invented after the word itself was used. The word Bible is derived from the Latin word biblio which simply means 'book'.

Other such backronyms include: FAITH, Fantastic-Adventures-In-Trusting-Him or FEAR, False-Evidence-Appearing-Real or GRACE, God's-Riches-At-Christ's-Expense