If you asked me to guess what the word "chalaza" means, I'd say, from its sound, that it would have to be an odd cactus-y looking plant that grows only in the Atacama desert and flowers once a decade, or an extinct language formerly spoken in the southern Caucasus mountains, or perhaps some sort of Levantine breadstick. It's an strange exotic word. But if then I told you that you've seen thousands, perhaps many thousands of chalazas (or chalazae) with your own eyes, and eaten as many, you'd be perplexed, even startled. Because you have eaten them.
Anyone who's cracked an egg has noticed two ropey white bands that extend from the yolk and are rooted in the transparent albumen.
Here's some more information about chalazae which I quote from Tim Birkhead's The Most Perfect Thing (2016), a detailed and most enthusiastic book all about eggs. "The role of the chalazae is to suspend the yolk within the albumen.... One end of each chalaza is attached to the ovum itself... and the other is firmly lodged in the layer of dense viscous albumen, which itself is attached to the shell membranes at the pointed and blunt ends of the egg. The chalazae allow the yolk to rotate when the egg is turned so that the embryo always remains on top of the yolk and within the inner liquid albumen layers. This self-righting ability is [necessary] because the embryo develops on the least dense side of the yolk. Keeping the embryo uppermost ensures that it is always closest to the parent's brook patch for maximum warmth, but also closest to the inner surface of the shell for maximum access to oxygen."
No chalazae, no chicks.
I'm astonished that although I have scrambled thousands of eggs, and certainly noticed the "ropey strands," I never gave them the slightest thought. How incurious of me!
Birkhead's book is a revelation. He is the egg man of our times. Occasionally he gets so carried away with his joy in the egg that he veers into unconscious comedy. I adore the phrase, "a renaissance in the study of eggshell pigmentation." Or, "guillemots are not quite unique in incubating shit-covered eggs." Or, "tinamous lay the most extraordinary and beautiful eggs." Or, "there is something sensual about eggs."
About the word chalaza: it's from the Greek meaning "small knot." Nor is it new: it entered the language (in Latinized form) in 1704.
Some practical information: the more prominent the chalazae, the fresher the egg.