It is probable that the gala of the Italians, and the galan of the Spaniards, are derived from the word "gal" which seems to be originally Celtic; hence, was insensibly formed gallant, which signifies a man forward, or eager to please.
"A Philosophical Dictionary, Volume 5 (of 10) From "The Works of Voltaire - A Contemporary Version""
François-Marie Arouet (AKA Voltaire) Commentator: John Morley Tobias Smollett H.G. Leigh
Admittedly there were only sixteen of the Lipans then left, men, women, and children, their chief, Juan galan, the son by a Lipan squaw, of the father of Garza galan, then the leading merchant of the town, and later a distinguished Governor of his State.
"The Red-Blooded Heroes of the Frontier"
Edgar Beecher Bronson
Jael I take to be most probably a softened form of Gale, from a stem referred to A.S. galan, to sing.
"Surnames as a Science"
Robert Ferguson