The word "couldst do" is an archaic spelling of "could do" and is pronounced as /kʊd(d)st duː/. The addition of "-st" to the end of "could" was a common practice in Early Modern English to indicate the second person singular of the verb. Today, this form of the verb is considered obsolete and is rarely used in modern English. However, it is still found in literary works of the past and can be studied as a part of the evolution of the English language.
"Couldst do" is an archaic phrase used in Middle English and early Modern English, like in the works of William Shakespeare. It is a combination of the verb "couldst" and the verb "do" in their infinitive forms. "Couldst" is the second-person singular past tense of the verb "can" and is used to indicate capability or possibility. "Do" is a versatile verb that can be used as a general action verb or as an auxiliary verb to form questions, negatives, or emphatic statements.
When put together, the phrase "couldst do" implies an ability or potential to perform an action expressed by the verb "do." It suggests that the subject has the capacity, skill, or opportunity to accomplish a particular task or achieve a desired outcome.
However, it is important to note that "couldst do" is no longer commonly used in contemporary English. It is considered outdated and has largely been replaced by modern equivalents such as "could do," "can do," or "are able to do."
The word "couldst do" is an archaic form of the phrase "could do".
Etymologically, "could" comes from the Old English word "cūðe", which means "knew" or "was able to". Over time, it evolved into "could" with the same meaning.
"Couldst" is the second person singular past tense of "could" in Middle English. It is derived from "could" and the suffix "-est", which was used to indicate the second person singular in many verbs during that period.
Finally, "do" is an Old English word that has survived with the same spelling to modern English. It means "to perform" or "to accomplish".
So, "couldst do" can be traced back to Middle English when it was used as a way to express the ability or potential action of the second person singular.