THE MEANING OF LOCUS FOCI AND TESTU
One of the striking typological characteristics of the guest
and service buildings on the Plan is the squares in the
center of these houses referred to varyingly as locus foci and
testu (fig. 358A-C). The first of these terms clearly refers
to the "fireplace" or open hearth in the middle of the floor
which heats the house. The second, testu, requires some
explanation. It has generally been taken to be an abbreviation
for the word testudo ("turtle" or "roof"),[226]
but I do
not think that this is the correct interpretation. Testu, as an
abbreviation for testudo, with no sign given to indicate that
a part of the word is missing, is not consistent with the
author's other abbreviations,[227]
and there is no reason to
assume that he departed from his normal procedure because
of the smallness of the space in which the word had
to be inscribed. The testu square in the Hospice for Pilgrims
and Paupers (fig. 358B) is large enough to accommodate
the whole word testudo and several other words if
necessary. What the scribe had in mind, in my opinion, was
the word testu, exactly as it is written—a rare yet perfectly
meaningful term.
Testu (indeclinable) means the "lid of a pot."[228]
It is
closely related to testa, which means "shell," either the
shell that covers a testaceous animal, the human skull
(testa hominis), or human artifacts of comparable construction,
such as clay bowls or pots.
Testudo is a derivative of
both these words. It shares with them the basic meaning
of "protective cover." In everyday language
testudo meant a
"tortoise" or "turtle"; in military language it was the name
for the protective covering formed when soldiers held their
shields overhead and locked them together. By analogy, in
architectural terminology—both classical and medieval—
testudo came to be the word used for "roof," usually a roof
of timber, but also by extension, a "vaulted roof."
[229]
Even supposing that the author of the Plan had in mind
testudo, rather than testu, it is unlikely that he referred to
the principal roof of the building; rather, he must have
meant a roof equal in size with the square in which
the term was written; and since this square is designated
both as testu and as locus foci, it is most probably to be understood
as "a protective shield above the hearth," the purpose
of which must have been to form a cover for a central smoke
outlet. Such openings in the roof above the hearth are, in
fact, a feature of the protohistoric and early medieval building
tradition just discussed, and they remained an intrinsic
part of vernacular buildings throughout the Middle Ages.