Words meaning "four", "fourth", "square" etc.

It's easy to confuse a group of Spanish, French and Italian words meaning "four", "fourth", "square" etc. The following are a few of them with relatively high frequency.

English ............... Spanish ....... French ................ Italian
four ..................... cuatro ......... quatre ................. quattro
fourth (ordinal) . cuarto ......... quatrième .......... quarto
square (shape) .. cuadrado .... carré .................... quadrato
painting .............. cuadro ........ [different word] . quadro

If traced to Proto-Indo-European, they are all cognates. But in Latin, or even within PIE, they already differentiated. For example, although Spanish cuadrado and cuadro are very close (even in Latin, where the former is just a participle of the latter), they have different etymons in Latin from those of cuatro and cuarto. In fact, cuarto, which has /r/ sound in the first syllable, is clearly different from all the other three. Regardless etymology, what tricks can we come up with to remember these words without confusing them? Since cuarto is very different due to its early letter r, you may make use of that fact. But the English equivalents have r everywhere (except in painting). One trick that does work is to notice the similarity between cuarto and English quarter. While cuarto can mean ordinal "fourth", it actually can also mean "one-fourth", which is exactly what quarter means. Then note that both cuadrado and English quandrant are mathematical concepts, so the meaning "square" of the former becomes obvious. Numeral cuatro is too frequent to require a mnemonic (i.e. rote memory suffices). The only one left is cuadro, which actually has a fairly high frequency so a mnemonic may not be needed, either.

Among the French words, quatrième is easy since suffix -ième obviously indicates an ordinal, hence "fourth". As to carré, some memory experts such as Harry Lorayne and Jerry Lucas, the authors of The Memory Book, most likely would encourage you to think of a gigantic square-shaped car, because the evoked image is provocative and logically improbable and so easy to remember. It may work in this case.

The Italian words are very similar to the Spanish. The most important difference is the first letter q instead of c. Since Italian is the most conservative in sound change from Latin among Romance languages according to historical linguists (e.g. Martin Maiden, the author of A Linguistic History of Italian) and the Latin etymons of these words start with q, it's understandable that these Italian words start with it, too.