What does Tamar mean?
From Hebrew tamar, 'date palm.' Borne by several biblical women (Genesis 38; 2 Samuel 13). A concrete noun; the palm's associations of uprightness, grace and fruitfulness are connotation rather than part of the etymology.
What does Yael mean?
From Hebrew ya'el, 'ibex' — a nimble, sure-footed wild mountain goat. The same name as the heroine Jael, who killed Sisera (Judges 4-5). A concrete noun; the 'strength of God' gloss seen on some sites is not the standard derivation.