What does Susannah mean?
From Hebrew 'shoshannah', from 'shoshan' meaning 'lily' (in modern Hebrew the same word can mean 'rose'). Reaches English via Greek 'Sousanna'. The original biblical sense is 'lily'.
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.