The silent 'b' in 'debt' was never spoken — scholars inserted it to reveal the Latin root 'debitum.'
Something, typically money, that is owed or due; a state of obligation to pay or repay someone.
From Old French 'dette' (debt), from Latin 'dēbitum' (something owed), neuter past participle of 'dēbēre' (to owe), a contraction of 'dē-' (from, away) + 'habēre' (to have). The literal meaning is 'something held away from' the creditor — something that has been taken and must be returned. The silent 'b' in the English spelling was inserted by Renaissance