Of the twenty-three canons issued by this Spanish council the second is noteworthy:
in all the churches of Spain and Gallica, the symbol of the faith of the Council of Constantinople, that is, of the 150 Fathers, be recited according to the form of the Eastern Churches, so that it be chanted in a loud voice by the people before the Lord's prayer is said. (Mansi, 9, 992)
It is strikingly clear that the Council of Toledo did not consciously alter the Ecumenical Creed. They obviously believed the Filioque was included in the original Nicene-Constantinopolitan Creed. The Filioque, both as doctrine and as found in various creedal statements and professions of faith, had so firmly rooted itself in the Latin West after Augustine that its authenticity and authority were simply taken for granted. (Haugh, pp. 27-29)
When I was Catholic, the local priest used to tell me that the reason the Latins use the filioque word is because there is no word such as through the Son in latin. They actually mean through the Son. It is just like the Our Father prayer in English.