lawyer is a person whose profession is to conduct lawsuits for clients or to advise them on their legal rights and obligations in other matters.
The word names the profession as a whole rather than any single role inside it, which is why the terms clustered around it are not interchangeable. In American usage attorney — short for attorney-at-law — names someone legally appointed to act on another's behalf, and is used almost synonymously with lawyer; counsel names the lawyer in the act of advising or representing, which is why a company has general counsel rather than a general lawyer. English and Commonwealth practice splits the work further: a solicitor handles client contact, documents, and preparation, while a barrister argues the case in court. In practice the title is bound to licensure, since admission to a bar is what permits a law graduate to appear for clients, and by American convention Esq. after a name signals that admission.
The word is native rather than borrowed. It formed in the late fourteenth century from Middle English lawe plus the occupational suffix -iere, appearing first as lauier, lawer, and lawere, with the -y- spelling taking over from the seventeenth century onward. Earlier English had other names for the role: Old English lahwita, literally a law-sage, and the mid-fourteenth-century man-of-law. Behind law itself sits Proto-Germanic lagam, "that which is laid down," from the Proto-Indo-European root legh-, "to lie down, lay" — the same image of fixity that gives English lay and ledge. In the King James New Testament the word carries a narrower sense still, an interpreter of Mosaic law.
"You ask your accountant questions, you tell your lawyer everything" ~ 📝Jim Goodman