Lagana is a Greek bread, made only once a year. The bread is served in Greece on the day that marks the start of Greek Orthodox Lent, called "Clean Monday" ("Kathara Deftera".)
It is flat and about 18 inches (45 cm) long, with rounded corners. It used to be unleavened, but recipes now use a small bit of yeast.
The dough is made with flour, water, yeast and olive oil. Sesame seeds are sprinkled on top just before baking (about 1 tablespoon of white sesame seeds, with a few black ones for colour, per loaf.) It is then baked at 350°F (180°C) for 30-40 minutes, until golden.
It is sold in bakeries.
It can be frozen, if it is frozen right after baking and cooling before it gets starts to get hard.
In classical Greek the word "Laganon" was neuter. When the Latin language absorbed the word, it became the Latin neuter of laganum, the plural of which is lagana.
The Romans used Laganum / Lagana to mean a sheet of dough, or a thin pancake.