Zen
Etymology
From Japanese zen, a rendering of Chinese chán, which in turn transliterates Sanskrit dhyāna (“meditation, contemplation”). So a single idea traveled from India to China to Japan to English, shedding syllables at each border. The tradition prizes meditation and sudden insight; popular English keeps mostly the calm.
noun · /ZEN/
A school of Buddhism centered on meditation and direct insight; loosely, a calm, unbothered attitude.
What it names
The disciplined pursuit of clarity through stillness — and, in casual English, the composure of someone who simply refuses to be rattled.
Example
Deadlines were collapsing around him, but he stayed weirdly zen about the whole thing.
Related idea
Serenity is a calm mood; Zen properly names a rigorous meditative discipline, though English often trims it down to “unbothered.”