cizí (Czech) comes from Old Czech cuzí, from Proto-Slavic ťuďь, from Gothic 𐌸𐌹𐌿𐌳𐌰, from Proto-Germanic þeudō, from Proto-Indo-European tewtéh₂, from Proto-Indo-European tewh₂- — to swell; to crowd; to be strong.
cizí (Czech): strange, unfamiliar; foreign