In a way that is beneficial, advantageous, or proper; appropriately or necessarily.
From 'behooveful' plus '-ly' adverb suffix. Built on the already-rare adjective 'behooveful,' this represents multiple layers of productive morphology stacked on an archaic root.
This word is so rare it's essentially a phantom—it demonstrates the principle that any adjective can theoretically become an adverb with '-ly,' but some combinations are so unusual they never actually get used.
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