Courgettes were first introduced in the UK in the early 1930s and soon several cookery writers began including this versatile vegetable in their recipes. Marcel Boulestin in 1931, translated the French term, courgette, as baby marrows, in spite of that the French word stuck and
The Oxford English Dictionary in its A-G supplement, gives the first
use of courgettes to E.Lucas in the same year, in
Elizabeth David in 1960, wrote her master book, French Provincial Cooking, and said:
"enterprising growers are supplying us with little courgettes as an
alternative to gigantic vegetable marrows".
Meanwhile in the US, the book A Fruit and Vegetable Buying Guide for Consumers
by Gerald Rowden Blountthe, published in 1933, tells us that the vegetable was known on some markets as vegetable marrow, Italian vegetable marrow, or zucchini.
Zucchini is the Italian term, its singular form, zucchina or zucchino means "little pumpkin". The term squash, gourd, comes from the Indian skutasquash also spelled as asquutasquash, meaning "green thing eaten green."
EDIT: I found an older reference which suggests that the harvesting of immature (baby) marrows was not unheard of in the 19th century. The book entitled The New and Improved Practical Gardener, and Modern Horticulturist by Charles McIntosh, published in London 1839, refers to marrows as vegetable-marrows and claims that it can be eaten at any stage of its growth. Of possible interest, the term culinary garden is used throughout the volume, and tomatoes in England were also known as love-apples.
Its Latin name, Cucurbita succada, also explains the origins of Italian word, zucca (pumpkin) and the diminutive term zucchini, although both vegetables belong to the same genus, cucurbita, they are quite different from each other, the latter being harvested in the summer months. Wikipedia however, informs us that zucchini belongs instead to the species Cucurbita pepo
The morphological differences within the species C. pepo are so vast
that its various subspecies and cultivars have been misidentified as
totally separate species. These vast differences are rooted in its
widespread geographic distribution. C. pepo is one of the oldest,
if not the oldest domesticated species. The oldest known
locations are in southern Mexico in Oaxaca 8,000-10,000 years ago and
Ocampo, Tamaulipas, Mexico about 7,000 years ago