The Irish god Nuada is known for three things: his magical sword, his sliver arm, and losing the kingship twice. HIs losses, however, define him in ways that show his quality.
The Irish goddess Boand is famous for two things: she is the mother of the young god Aengus, whom she carried to term in a single (nine-month-long) day, and the river Boyne is named for her, after she caused it to gush forth from a magical well.
You might wonder, why are salmon wise? Their ability to return to their birthplace to spawn may have given rise to the idea that they had special knowledge. Their travelling between salt and fresh water shows an adaptability most fish don’t have, and their jumping (immortalized in the Celtic warrior’s salmon leap) is impressive, and gives them their English name (from Latin salire, to jump).
In Irish finn means “fair, bright, white, lustrous, light-hued” (MacKillop: 226), and the Welsh gwyn is similar in meaning, with overtones of sacredness. Similarly, the Gaulish god, Vindonnus, gets his name from a root meaning either “clear light” (Green: 32) or “white, blessed” (Deo Mercurio). Coming at it from another direction, Daithai O hOgain has linked Finn/Vind with the Germanic find and Latin vid, words connected to sight and discovery (208).
From this it has been a short step to assuming a god, *Vindos, lying behind these various figures. However, like the “theoretical goddess” Rigantona, the names is a linguistic construct, and we have no evidence of a cult of Vindos.
Where did the idea that Flidais rode in a chariot drawn by deer come from? It’s not in her main legend, the Táin Bó Flidais, nor in the follow-on story, the Táin Bó Cúailnge. It’s an attractive image, bringing to mind the Middle Eastern goddesses with their lion-drawn chariots, Freyja with her cats, and Nerthus in her wagon drawn by heifers.