"resembling an oyster," 1840, with -an + Latinized form of Greek ostrakios, from ostreion "oyster," from PIE *ost-r-, from root *ost- "bone." Related ostraceous (by 1834).
Entries linking to ostracean
-an
word-forming element meaning "pertaining to," from Latin -anus, adjective suffix, in some cases via French -ain, -en. From PIE *-no-.