Thickly derives from Middle English thikly, formed by combining the adjective thik with the adverbial suffix -ly, which comes from Old English -līċ, ultimately from Proto-Germanic þekuz and Proto-Indo-European teg-, meaning to cover or be dense.
thickly (English): In a thick manner
Definitions
In a thick manner
Ancestry of “thickly”, step by step
thickly traces back through two separate lines of ancestry.