Tra comes from a Sanskrit word trayate that means "to liberate."
Frasquita and Mercedes join in the "Tra la la la" of the refrain.
Occasionally the accusative of direction is used after tra, when this seems useful for emphasis, or to remove ambiguity.
He made his friend repeat the performance, called him a daisy, and tra la la'd to his heart's content.
Tra la fenestro antaŭ si Johano rigardas la virojn kaj la virinojn sur la strato.
Tra is tolerably rich in the remains of ancient houses, of which the drawing shows an example.