Luke 12:51

The noun διαμερισμός, derived from the verb διαμερίζω (“to divide, distribute”), denotes both the act of apportioning (e.g., in territorial or cultic contexts such as LXX Ezek. 48:19; Jos. Ant. 10.11.7). The word was used of the soldiers dividing up the garments.

διαμερισμός does not specifically mean "dividing in two." While it does refer to the act of dividing or partitioning, it more generally implies a division into parts, not necessarily two equal parts.

If you want a Greek word that specifically refers to dividing into two parts, you would use the verb χωρίζω (meaning "to separate" or "to divide"), especially in the context of splitting something into two distinct portions. Another possible word is διάσπαση (from διάσπασις), which can imply a splitting or cleaving into two.