The correct spelling of the word "coccygerector" is a bit tricky to understand without using IPA phonetic transcription. The IPA symbols in this word are /kɒksɪdʒɛrɛktər/. The first syllable "coccy" refers to the coccyx bone at the base of the spine, which is pronounced as "kocks-ee". The second half, "gerector", comes from Latin and means "to straighten", pronounced as "juh-rek-tor". Therefore, "coccygerector" means a muscle that straightens the coccyx bone.
Musculus extensor coccygis.
A practical medical dictionary. By Stedman, Thomas Lathrop. Published 1920.