That doesn't seem like the type of thing you would want to keyword. The point of keywords is that they are a repeated mechanical pattern that players can mentally shortcut after seeing and playing with cards featuring it for a while.

This ability would be extremely oppressing in larger numbers and lower cost cards, making it unfit for prominent use, especially at lower rarities - which are what keywords are generally meant for as they lessen the overall mechanical nuance and complexity by generalizing/standardizing abilities and lowering the amount of raw rules text (where reminder texts don't count).

I think what you might be looking for here is a 'flavor word' as seen in cards such as Air-Cult Elemental and Blink Dog.