-cule

word-forming element meaning "small, little" (in capsule, module, etc.), from French -ule, from Latin diminutive suffix -ulus (fem. -ula, neuter -ulum), from PIE *-(o)lo-, from *-lo-, secondary suffix forming diminutives, which also is the source of the first element in native diminutive suffix -ling.

"rod-shaped bacterium," 1877, medical Latin, from Late Latin bacillus "wand," literally "little staff," diminutive of baculum "a stick, staff, walking stick," from PIE *bak- "staff" (also source of Greek bakterion; see bacteria) + instrumentive suffix -culo (see -cule). It was introduced as a term in bacteriology in 1853 by German botanist Ferdinand Cohn (1828-1898).