You have received your great-grandfather John MAIR's death certificate. The certificate tells you he died of "phlegmonous erysipelas." In reading your Grand-aunt Martha's diary you learn that her sister was afflicted with "ablepsy" and that your Uncle Alfred suffered from "dropsy." In the diary you also read that John MAIR worked as a "dyker" in his native Scotland. Martha's husband was a "cordwainer" and Uncle Alfred was working as a "huckster."
Genealogists frequently encounter archaic, foreign, regional, or merely unfamiliar terminology for causes of death and illnesses, as well as for our ancestors' occupations.
ILLNESSES, DISEASES, AND OTHER ARCHAIC MEDICAL TERMINOLOGY
The following websites are among many I've used over the years to learn the meanings of terms no longer in common use or with which I wasn't familiar:
http://www.neonatology.org/classics/old.terms.html (Terms concerning neonatology.)
http://www.antiquusmorbus.com/Index.htm (Archaic medical terms.)
DISASTERS—NATURAL and MANMADE
Sometimes the factors involved in ancestral deaths could indicate that family members died as the result of a disaster. Disasters should be considered when multiple family members died at exactly the same time. A disaster could be an earthquake, flood, fire, shipwreck, mining accident, train wreck, etc.
Deaths of more than one person over a short time period (but not necessarily on the same day), especially when children are involved, might indicate an epidemic caused by the flu, typhoid, yellow fever, or any other contagious disease.
OBSOLETE AND UNFAMILIAR OCCUPATIONAL TERMS
Unfamiliar occupational terms and obsolete occupational terminology often varies from country to country or even from region to region within a country.
http://www.olivetreegenealogy.com/misc/occupations.shtml (Medieval English and early New World.)
http://rmhh.co.uk/occup/index.html (United Kingdom.)
http://www.worldroots.com/~brigitte/occupat.htm (German occupations and illnesses.)
A quick review of the websites referenced here reveals that your great-grandfather died of a severe inflammation and fever, Martha's sister was blind, and Uncle Alfred had swelling or fluid retention (edema). Your great-grandfather worked as a stonemason in Scotland. Martha's husband was a shoemaker and Uncle Alfred sold small wares.