"So we can look at, for example, Old Irish, where they said tó to mean yes"
Really? In modern Irish we substitute Tá for yes but it's not really yes. We don't have yes or no, we repeat the verb of the question positively or negatively. Tá is kind of 'am', níl 'am not' like
"Are you going to watch Mrs Browns Boys tonight?"
"I am not."
Are they really comparable? Maybe somewhere along the line Tá (pronounced 'taw') was taken for 'yes'.
Really? In modern Irish we substitute Tá for yes but it's not really yes. We don't have yes or no, we repeat the verb of the question positively or negatively. Tá is kind of 'am', níl 'am not' like
"Are you going to watch Mrs Browns Boys tonight?" "I am not."
Are they really comparable? Maybe somewhere along the line Tá (pronounced 'taw') was taken for 'yes'.