Because
Elizabeth is the English version of the name, taken from the Greek
Elisabet. In Hebrew it's
'Elisheva — ' "God is an oath," the second element said by Klein to be related to shivah (fem. sheva) "seven," and to nishba "he swore," originally "he bound himself by (the sacred number) seven" ' (Online Etymology).
There is no "beth" sound in the original name; in fact, it isn't present in many versions of the name, such as
Isabel,
Isabella,
Elisabetta, or
Yelizaveta.
Alexandrina, Annabella, Clementine, Charlotte, Emilienne, Florence, Frederica, Katharina, Mary (May), Maud, Penelope, Rosamund, Theodora (Teddy).
Aubrey, Axel, Benedict, Bertrand (Bertie), Cuthbert, Dashiell, Everard, John (Jack) Leopold (Leo), Magnus, Matthias, Maximilian (Max), Wilfred.This message was edited 12/2/2015, 3:16 PM