stereotyped epithet; conventional poetic epithet
A fixed, conventional epithet used in classical Japanese poetry (waka) to modify a particular word, often serving as a rhetorical ornament. Not used in everyday speech.
"Ashibiki no" is a stereotyped epithet that modifies "yama" (mountain).
In waka poetry, a stereotyped epithet is placed before a specific word to create a poetic effect.