Sirach vs Ecclesiasticus

Sirach and Ecclesiasticus both are nouns.

Word	Noun	Adjective	Verb	Adverb
Sirach	Yes	No	No	No
Ecclesiasticus	Yes	No	No	No

As nouns, Sirach and Ecclesiasticus are synonyms defined as:

Sirach and Ecclesiasticus: an Apocryphal book mainly of maxims (resembling Proverbs in that respect)

Other synonyms of Sirach include Ben Sira, Wisdom of Jesus the Son of Sirach.

Sirach (noun)	Ecclesiasticus (noun)
an Apocryphal book mainly of maxims (resembling Proverbs in that respect)	an Apocryphal book mainly of maxims (resembling Proverbs in that respect)