The term Old Catholic Church originated with groups that split from the Roman Catholic Church over certain doctrines, most importantly that of Papal Infallibility. These churches are not in full communion with the Holy See of Rome. Nevertheless, according to Roman Catholic teaching the Old Catholic churches of the Utrecht Union have maintained apostolic succession and valid sacraments. The formation of the Old Catholic communion of Germans, Austrians and Swiss began in 1870 at a public meeting held in Nuremberg under the leadership of Ignaz von Döllinger, following the First Vatican Council. Four years later episcopal succession was established with the ordination of an Old Catholic German bishop by a prelate of the Church of Utrecht. In line with the “Declaration of Utrecht” of 1889, they accept the first seven ecumenical councils and doctrine formulated before 1054, but reject communion with the pope and a number of other Roman Catholic doctrines and practices. 
The term “Old Catholic” was first used in 1853 to describe the members of the See of Utrecht who did not recognize any claimed “infallible” papal authority. Later Catholics who disagreed with the doctrine of Papal Infallibility as made official by the First Vatican Council (1870) had no bishop and so joined with Utrecht to form the Union of Utrecht.
There are quite literally thousands of independent clergy, that have been ordained in an manner maintaining apostolic succession and valid sacraments, in the tradition of the Old Catholic Church, but are not in communion with that church. These clergy have quite valid lines of apostolic succession identical to some of those lines held by clergy of the Roman church as well as several of the Orthodox lines. And while operating under one or more of the classifications below, this group is generally known as the Independent Sacramental movement.
Independent Sacramental Movement
The Independent Sacramental Movement (ISM) refers to the extremely loose collection of orders, churches, jurisdictions, and freelance clergy made up of sacramental Christians who are not part of the historic sacramental denominations. Many in the ISM owe their origins to schisms from Roman Catholic, Old Catholic, Anglican, and Orthodox churches, and generally claim to preserve the historical episcopate or apostolic succession, though this claim would be seriously questioned, if not rejected, by the ecclesiastical authorities of Rome, Constantinople, Utrecht, and Canterbury. Utrecht and some jurisdictions within the Anglican Communion have engaged in ecumenical conversation with some groups which could be included in the ISM. Groups which are structurally similar but without claiming the apostolic succession may also be classed as part of the ISM.
Groups within the ISM (often known as Independent Catholic, Old Catholic, Liberal Catholic, Autocephalous Orthodox, Free Sacramental, etc.) tend to share a number of characteristics: small groups and/or solitary clergy, centrality of the sacramental life (especially the Eucharist), a mediatory priesthood mostly composed of volunteers, ordination potentially available to a significant percentage of the membership, and experimentation in theology, liturgy, and/or church structure.
The term was popularized by John Plummer in his book “The Many Paths of the Independent Sacramental Movement”, although it was earlier used by Richard Smoley in “Inner Christianity,” and perhaps first used in the mid-1970s by a short-lived cooperative organization called the Synod of Independent Sacramental Churches. ISM groups range from the broadly inclusive (including marriage of same-sex couples and the ordination of women) to the socially conservative; also from the traditionally orthodox to the esoteric, although the term is most commonly employed to refer to the liberal end of the spectrum. While the term “Independent Sacramental” originated as an etic description, it has been used increasingly as an emic self-description by members of some of these churches and groups.