Shameless means not embarrassed by behaviour that should shame you. Shameless self-promotion, utterly shameless, a shameless lie.
It is a strong criticism, and yet shameless self-promotion is used cheerfully about oneself, which takes the sting out. Shameless is not the same as brave: it means the person feels no shame rather than that they overcame it. Note shameful, which describes the act, and shameless, which describes the person — the two are constantly swapped; and shamefaced, meaning visibly ashamed.
1adjectiveshamelessNot embarrassed by behaviour that should cause shame.
“He told a shameless lie to the teacher and didn't even blush.”
shameless is a quality of feeling no shame.
Old English scamleas is shame plus -less. Shame is Germanic and its deeper root may mean covering, from the instinct to hide the face — which is exactly what shamefaced describes.
Middle English
schameles
English, today
shameless
Built from
From Middle English schameles. From Middle English schameles, shameles, from Old English sċamlēas, sċeamlēas (“without shame; shameless”), from Proto-Germanic skamalausaz (“shameless”), equivalent to shame + less. Cognate with West Frisian skamteleas (“shameless”), Dutch schaamteloos (“shameless”), German schamlos (“shameless”), Danish skamløs (“shameless”), Swedish skamlös (“shameless”), Icelandic skammlaus (“shameless; unashamed”).
Etymology from Wiktionary, CC BY-SA