From Middle English seisin, seysen, from Old French seisin, from the verb seisir, from Early Medieval Latin sacīre, from the same Proto-Indo-European root as Gothic 𐍃𐌰𐍄𐌾𐌰𐌽 (satjan) and Old English settan. More at seize, seise.
Practice speaking and memorizing "seisin" and many other words and sentences in English.