Check with a large public library for a copy. Boggles are evil spirits, goblins or bugbears. Bogyman is still in standard usage. The root word is Middle english bugge meaning spirit. Efreet is alternative spelling of afreet, a Moslem supernatural being typically unfriendly toward humans.
Wraiths are ghosts or sometimes spirits that appear to warn of evils to come.
The word orc denoted a sea monster which does not seem appropriate in context. But it might be worth looking for a possible connection to the Orkneys. The Vikings who settled in that area were responsible for the complete destruction of Columba's monastery at Iona and sacking Lindisfarne, which was a major center of culture. As a people they were the scourge and terror of the Christian church in Europe. Another possiblity would be to check where Tolkien derived his orcs.