sternly
adv. US //ˈstɝnɫi// UK //stˈɜːnli// stern·ly
From Middle English sternly, sternely, sterneliche, sturnely, sturneliche, from Old English stirnlīċe, styrnlīċe, stiernlīċe (“harshly; severely; sternly”), equivalent to stern + -ly.