Medical professionals need terms which are neutral, unemotional and free from the connotations of normal, vernaculat usage. The word heart is an interesting example of the problem of keeping scientific vocabulary as objective as possible.
A doctor today might inform you that you have a heart condition but would probably use cardiac (from the Greek) in a letter or formal note. In old medical texts he would have written of a cordial failure. We notice that the shift is towards Latinate terms and that Greek is often employed - as in the many terms ending in ology. This is to avoid the subjectivity of our native words.
In Middle English, around 1400, the word cordial entered the language, derived from Latin cor and cordialis and meant of the heart or pertaining to the heart. It functioned in exactly the same way as cardiac does today.
The shift was then towards a more metaphorical sense via cordial as a drink which was believed to strengthen the heart - even one laced with opium as was Godfrey's Cordial. That sense (as a noun) has been retained although it refers to different syrups and liquids depending on country. The adjective has become entirely figurative: when you give a visitor a cordial welcome, you are not necessarily offering a drink.
Fortunately for medicine, the word cardiac has retained its objectivity: you do not give your friend a cardiac hug! Perhaps a hearty one.
Yet, we might swap our usual CUPPA for a glass of heart-warming cordial now that the weather is colder.
