Endurance, doubled. The two-character version of 忍.

What a Japanese person actually thinks
Sober and slightly stoic. Reads as someone who has had to wait out something difficult. No frills.

Naturalness●●●●●

Common word.

Coolness●●●●●

Both characters carry the heart radical (心/忄), which gives the pair a nice internal logic.

Nothing embarrassing lurking in here.

忍 nin
to endure; a blade over the heart

The single character is more striking as a tattoo, and the blade-over-heart etymology gives you something to say.

忍耐

Orientation: vertical

Mincho.