| Aife | Celtic | F | A great warrior woman of myth |
| Ailidh | Celtic | F | Kind |
| Ailill | Celtic | F | Mythical king of Connaught |
| Aina | Celtic | F | Joy |
| Airell | Celtic | M | Nobleman |
| Airic | Celtic | F | Agreeable |
| Aithne | Celtic | F | Fire |
| Alan | Celtic | M | Handsome |
| Alane | Celtic | F | Fair |
| Alanson | Celtic | M | Son of Allan |
| Alastrine | Celtic | F | Defender of mankind |
| Albion | Celtic | M | White cliffs |
| Aleen | Celtic | F | Fair |
| Aleena | Celtic | F | Fair |
| Alena | Celtic | F | Fair |
| Alene | Celtic | F | Fair |
| Alice | Celtic | F | Truthful |
| Aline | Celtic | F | Fair |
| Allan | Celtic | M | Handsome |
| Allen | Celtic | M | Handsome |
| Allena | Celtic | F | Fair |
| Allene | Celtic | F | Attractive |
| Allyn | Celtic | M | Handsome |
| Alys | Celtic | F | Noble |
| Anant | Celtic | M | From the stream |
| Andraste | Celtic | F | Victory |
| Anghus | Celtic | M | Exceptionally strong |
| Annan | Celtic | M | From the stream |
| Annwfn | Celtic | F | Mythical name of The Otherworld |
| Annwn | Celtic | F | Mythical name of The Otherworld |
| Anwell | Celtic | M | Beloved |
| Anwyl | Celtic | M | Beloved |
| Anyon | Celtic | M | Anvil |
| Aod | Celtic | M | Mythical son of Lyr |
| Aodh | Celtic | M | Fire |
| Aodhan | Celtic | M | Fire |
| Aonghus | Celtic | M | Exceptionally strong |
| Ap Owen | Celtic | M | Son of Owen |
| Aphria | Celtic | F | Agreeable |
| Arawn | Celtic | M | Mythical king of the Underworld |
| Arden | Celtic | M | Ardent |
| Arden | Celtic | F | Valley of the eagle |
| Ardena | Celtic | F | Lofty or eager |
| Ardene | Celtic | F | Lofty or eager |
| Ardra | Celtic | F | Noble |
| Arela | Celtic | F | An oath |
| Arienh | Celtic | F | Oath |
| Arlan | Celtic | M | Pledge or oath |
| Arlana | Celtic | F | Pledge or oath |
| Arlin | Celtic | M | Pledge or oath |
| Arlina | Celtic | F | Pledge or oath |
| Arline | Celtic | F | Pledge or oath |
| Arlyn | Celtic | M | Pledge or oath |
| Arthur | Celtic | M | Bear |
| Arturo | Celtic | M | Noble |
| Attie | Celtic | M | Strong as a bear |
| Atty | Celtic | M | Strong as a bear |