What is the X in X-mas?
"pertaining to walking;" also "shifting, not permanent," 1620s, from Latin ambulatorius "of or pertaining to a walker; movable," from ambulator, agent noun from past participle stem of ambulare "to walk" (see amble). Middle English had ambulary "movable" (mid-15c.).
from Medieval Latin ambulatorium, from Latin ambulatorius "movable," from ambulare (see amble).
ambulatory am·bu·la·to·ry (ām'byə-lə-tôr'ē)
Of, relating to, or adapted for walking.
Capable of walking; not bedridden.
in architecture, continuation of the aisled spaces on either side of the nave (central part of the church) around the apse (semicircular projection at the east end of the church) or chancel (east end of the church where the main altar stands) to form a continuous processional way. The ambulatory often provided improved sites for the numerous altars for saints, which formerly were located along a crowded corridor behind the high altar; the altars are reached through circular arches piercing the curved outer wall of the ambulatory.