of Latin spelling. For example, in a radical break from the traditional system, a word such as ⟨viridiarium⟩ 'orchard' now had to be read aloud precisely as it was spelled rather than */verdʒjær/ (later spelled as ). Such a radical change had the effect of rendering Latin sermons completely unintelligible to the general romance-speaking public, which prompted officials a few years later, at the Third Council of Tours, to instruct priests to read sermons aloud in the old way, in or 'plain Roman[ce] speech'. As there was now no unambiguous way to indicate whether a given text was to be read aloud as Latin or Romance, various attempts were made in France to devise a new orthography for the latter; among the earliest examples are parts of the Oaths of Strasbourg and the Sequence of Saint Eulalia (see below). Non-Latin influences Gaulish Some Gaulish words influenced Vulgar Latin and, through this, other Romance languages. For example, classical Latin was uniformly replaced in Vulgar Latin by 'nag, work horse', derived from Gaulish (cf. Welsh , Breton ), yielding , Occitan (), Catalan , Spanish , Portuguese , Italian , Romanian , and, by extension, English cavalry and chivalry (both via different forms of [Old] French). An estimated 200 words of Gaulish etymology survive in Modern French, for example , 'oak tree', and , 'plough'. Within historical phonology and studies of language contact, various phonological changes have been posited as caused by a Gaulish substrate, although there is some debate. One of these is considered certain, because this fact is clearly attested in the Gaulish-language epigraphy on the pottery found at la Graufesenque ( 1st century). There, the Greek word (written in Latin) appears as . The consonant clusters /ps/ and /pt/ shifted to /xs/ and /xt/, e.g. > *kaxsa > caisse ( Italian ) or captīvus > *kaxtivus > (mod. chétif; cf. Irish cacht 'servant'; ≠ Italian , Portuguese , Spanish ). This phonetic evolution is common in its later stages with the shift of the Latin cluster /kt/ in Old French ( > fait, ≠ Italian , Portuguese , Spanish ; or lactem* > lait, ≠ Italian , Portuguese , Spanish ). This means that both /pt/ and /kt/ must have first merged into /kt/ in the history of Old French, after which this /kt/ shifted to /xt/. In parallel, /ps/ and /ks/ merged into /ks/ before shifting to /xs/,