The prefix [ipsi-] arises from the Latin [ipse] meaning "self" or "same". In medical terminology this prefix is used in the words "ipsilateral" and ipsilaterally" to denote an organ or structure in the "same side of the body" (left or right) as another structure that is being referred to.

A synonym for ipsilateral is [homolateral]; the antonym for the term is [contralateral].

The anterior cerebral arteries are one of the two paired terminal branches of the internal carotid artery. Each anterior cerebral artery supplies arterial blood to the brain beyond the arterial circle of Willis. The vascular territory of the anterior cerebral artery supplies the medial surfaces of the frontal and parietal cerebral lobes as well as the medial border of the same lobes.

The anterior cerebral artery gives off the orbitofrontal artery and then divides into two callosal arteries, the pericallosal artery and the callosomarginal artery. From these arteries arise all the other branches that form the vascular territory of the anterior cerebral artery.

There are many anatomical variations of the anterior cerebral artery, as described here.

Image modified from the original (in the public domain) by Sobotta (1945)

The medical term thrombus arises from the Greek [θρόμβος] (pronounced thrombos) meaning "a lump", "a piece of milk curd", or a "clot". This Greek term was later adopted in Latin [thrombus] and is used in this unchanged form today. The plural for thrombus is [thrombi].  A synonymous Latin term is [coagulum] (pl. coagula).

In medicine, a thrombus is a blood clot that has the connotation of being stationary, fixed to a vessel wall. If this blood clot were to be freed and start moving with the blood flow, then the clot should be called an "embolus" (Lat; pl. emboli).

Because of its anatomical characteristics. in the presence of atrial fibrillation, the left atrial appendage is particularly prone to the formation of thrombi, which can embolize and cause brain strokes.

The root term for this word is [-thromb-]. Examples of its use are:

• Thrombosis:  The suffix [-osis] means "condition" with the connotation of "many". A condition of multiple thrombi
• Thrombocytopenia: A combination of root terms; the root term  [-cyt-] means "cell" and the suffix [-(o)penia] means "a deficiency". A deficiency of platelets (the "clotting" cells)

Sources:
1. "The Origin of Medical Terms" Skinner, HA 1970 Hafner Publishing Co.
2. "Medical Meanings - A Glossary of Word Origins" Haubrich, WD. ACP Philadelphia

First used by Galen of Pergamon (129AD - 200AD) the word [etiology] is of Greek origin. [α?τία] or [aitia], meaning "cause", and [λογία] or [-ology], meaning "study of". Etiology is the "study of cause". In medicine this word I used to denote the study of the causes for a pathology, disease, or condition.

Because of its Greek origin, Skinner (1970) states that the proper way of spelling this term should be ?tiology, but the initial "a" has been discarded through use.

There are many pathologies of unknown origin. In this case the word to use would be [idiopathic] or [idiopathy] meaning "of unknown cause"