Commentaire sur Les Psaumes 88:16

and close to sudden death Heb. וגוע מנער, dying from the strangulation of sudden death, as (Exod. 14:27): “and the Lord strangled (וינער).” Menachem (p. 123) defines וינער as an expression of beating, as (Isa. 33:15): “who shakes (נוער) his hands from taking hold of bribe”; (Isa. 52:2), “Shake yourself (התנערי) from the dust, arise”; (Isa. 1:31), “And the[ir] strength will become as tow (לנערת)”; (Job 38: 13), “so that the wicked will be shaken (וינערו) from it”; (Neh. 5:13), “even thus may he be shaken out (נעור) and emptied.”

it is well-founded Heb. אפונה. Your fear is settled and based in my heart. אפוּנה is an expression of (Prov. 25:11): “a word spoken with proper basis (אפניו)”; on its basis.