What is the meaning of Sinister?

Inauspicious, ominous, unlucky, illegitimate (as in bar sinister).

Evil or seemingly evil; indicating lurking danger or harm.

Of the left side.

On the left side of a shield from the wearer's standpoint, and the right side to the viewer.

Wrong, as springing from indirection or obliquity; perverse; dishonest.

sinister

sinister

left

perverse, bad; or adverse, hostile

auspicious (for Romans) or inauspicious (for Greeks)

Source: wiktionary.org